This application claims priority of Korea patent Application No. 2000-84034, filed on Dec. 28, 2000.
(a) Field of the Invention
The present invention relates to a method for diagnosing a battery of a vehicle and a system thereof, and more particularly to a method for diagnosing a battery of a vehicle to detect deterioration of a battery of a vehicle earlier and more precisely and a system thereof.
(b) Description of the Related Art
An internal combustion engine, such as a gasoline engine used for a power source of a vehicle, transforms heat energy generated in combustion into dynamic energy to be used as a driving power for a vehicle.
But the exhaust gas generated during combustion includes various noxious gases such as nitrogen oxide, and carbon monoxide and hydrocarbons are produced by incomplete combustion such that these gases become a principal cause of air pollution.
Especially in these days when the number of automotive vehicles has increased explosively, air pollution caused by the exhaust gas of vehicles has become a principal social issue.
Therefore, vehicles that do not exhaust such noxious gases and that do not use limited natural resources, such as electric vehicles and solar powered vehicles that utilize solar energy as a power source, have been discussed, and research and development for such vehicles has greatly progressed to a point where such vehicles are close to being put into practical use.
An electric vehicle includes a battery of which the charged energy is used as a power source; a motor that generates driving force of a vehicle, the motor being operated by the charged energy of the battery; and a controlling apparatus to control the battery and the motor.
In addition, a solar powered vehicle includes solar cells that generate electric energy from solar energy, a battery to store the electric energy, a motor to drive the vehicle, and a controller for controlling the above-mentioned parts. A solar powered vehicle is different from an electric vehicle in that it includes solar cells to transform solar energy to electric energy and therefore charge the battery.
Solar powered vehicles are under continuing research and development so that they may be put to practical use because they attract considerable attention for their pollution-free characteristics. Functioning and performance of the above-mentioned parts of solar powered vehicles are required to be precisely monitored.
A battery of a vehicle is an important power reservoir and source, especially when the vehicle is an electric vehicle or a solar powered vehicle. Therefore, the current charging and/or charge state of the battery has to be checked and determined to prevent possible malfunction caused by excessive discharging of the battery, and to prevent the possibility of accidents that may occur when the battery is in an abnormal state.
A conventional battery for an electric or a solar powered vehicle includes a plurality of modules, where each module includes a number of cells. For example, each module includes ten (10) cells, where each cell stores 1.2 volts when charged, and twenty-six (26) modules are included in the battery so that the potential output voltage of the battery is over 300 volts.
According to the prior art, in order to determine whether a battery is malfunctioning, an absolute value of the difference between a maximum voltage and a minimum voltage of included modules is measured and compared with a predetermined reference voltage difference (for example, 1V), and the battery is determined to be malfunctioning if the absolute value is greater than the predetermined reference voltage difference, which is a condition for changing the charging mode.
FIGS. 1a and 1b shows examples of voltage distribution measured according to the prior art.
The dotted line in the lower graph of FIG. 1 is a normal distribution curve fitted to the module voltage distribution.
FIG. 1a shows the voltage distribution of modules uniformly spread in a region of xcex94V, in which case there is no problem in determining malfunctioning of a battery.
However, FIG. 1b shows the voltage distribution of modules where all are concentrated around an average value except one. In such a case as shown in FIG. 1b, the module of which the voltage is far from the average value is probably malfunctioning or is deteriorated, but according to the prior art, the malfunctioning/deterioration cannot be detected if the difference between the maximum and the minimum value of voltages is less than a predetermined reference voltage difference. Therefore, the deteriorated module suffers damage for a long time until the deterioration is detected, and thereby the whole battery can deteriorate so much that it cannot work to drive a vehicle.
According to the prior art, if the voltages of the modules do not satisfy the condition for changing charging mode, the charging is not stopped even when the battery malfunctions, and therefore pressure and temperature increase in the malfunctioning cell because the malfunctioning cell will have high resistance, and furthermore, a fire may possibly be caused because of the heat.
Therefore, the present invention has been made in an effort to improve accuracy of determining whether a battery of a vehicle malfunctions or is deteriorated.
It is an objective of the present invention to provide a method to monitor battery function with more accuracy, and to determine if the battery may be malfunctioning and which module may be malfunctioning.
To achieve the above objective this invention provides a method for diagnosing a battery of a vehicle, the battery including a plurality of modules, the method comprising:
starting charging of a battery; detecting voltage of each module being charged; calculating an average voltage and at least one of a maximum voltage and a minimum voltage of the modules; calculating an absolute value of a difference between the average voltage and at least one of the maximum and the minimum voltages; and determining whether the battery may be malfunctioning by comparing the absolute value with a predetermined reference value.
The method for diagnosing the battery is performed by a system for diagnosing a battery of a vehicle of the present invention, the system comprising:
a battery charging part;
a charging control part for controlling the battery charging part in order to charge the battery to a predetermined voltage;
a battery voltage detecting part for detecting voltages of the modules of the battery; and
a display part for displaying a current state of the battery:
wherein the charging control part, after the receiving module voltages from the battery voltage detecting part, calculates an average voltage and at least one of a maximum and the minimum voltage of the modules, and an absolute value of a difference between the average voltage and at least one of the maximum and the minimum voltages, and then determines whether the battery may be malfunctioning by comparing the absolute value with a predetermined reference value.
If it is determined that the battery may be malfunctioning, the charging control part changes a charging mode or warns of the possibility of malfunction by activating the display part.